The present application finds particular application in cruise-control systems commercial vehicle systems, particularly involving heavy-duty vehicles. However, it will be appreciated that the described technique may also find application in other motor control systems, other commercial vehicle systems, or other cruise control vehicle systems.
Heavy-duty vehicles, such as large trucks or tractor-trailers, busses, and the like often employ set-speed cruise control (SSCC) systems that govern acceleration when turned on. Additionally, an adaptive cruise control (ACC) system may be employed to control vehicle speed via foundation braking, engine torque reduction, and vehicle retarder to affect distance to a target forward vehicle. Conventional systems require the SSCC to be in an ON state in order for the ACC to be in an ON state. Disengaging the SSCC, without driver consent or knowledge, during an acceleration control event can cause the ACC to stop acceleration control (braking). In such cases, all ACC braking ceases regardless of any forward vehicle situation (e.g., a vehicle in front of the commercial vehicle using the ACC system).
Some examples in which vehicle set speed cruise control may disengage without intentional direct driver input or knowledge include: during ACC foundation braking; a set speed cruise control fault; the vehicle being out of gear; low engine speed; non-maintainable engine speed; time of day (e.g., where restrictions on the use of cruise control after dusk apply); headlights or windshield wipers (e.g., activation of such systems implies hazardous driving conditions during which ACC may not be permitted); automatic transmission shift; external air temperature (e.g., cold conditions wherein cruise control may be deemed unsafe and therefore not permitted); etc.
A problem with conventional ACC systems is that they typically are only in an ON state when the SSCC is in an ON state, and they shut off when the SSCC shuts OFF. When the SSCC is shut off due to an ACC deceleration (e.g., due to a detected forward vehicle that is too close), conventional systems do not recognize that the SSCC shutoff is a result of the ACC deceleration event, and that the ACC should remain on to complete the deceleration event. Rather, conventional ACC systems trigger an SSCC shutoff, and then detect that the SSCC is shut off and in turn deactivates the ACC in response thereto.
The present invention application provides new and improved adaptive cruise control systems and methods for heavy-duty vehicles that permit the ACC system to continue operating in desired circumstances after SSCC shutoff, which overcome the above-referenced problems and others.